Easy Construction of Strobe Lights as used in Police Vehicles Explained

This simple electronic home project of LED strobe lights can be used to add a beautiful pulsating light show during party gatherings or simply may be used in your car as a stroboscopic external roof lights to make some heads turn (WHERE LEGAL) over the busy streets. Let's read it here.

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What are Stroboscopic Lights

In many Hollywood action movies we see the use of chasing police vehicles with red and blue overhead lamps flashing in a most peculiar and interesting fashion. These glamorous lighting effects are produced by a stroboscopic device or strobe lights, also called strobes in short. The device produces short pulses of high intensity dazzling light. The frequency of these pulses may be adjustable. In fact, it’s the strobe lights used in police vehicles that make the police cars and vans so attractive and intriguing to the common eye.

You will also find the use of these lights in discotheques, rave parties etc. to make the party atmosphere more sensational. Other serious applications of strobe lights include the study of motion of fast moving objects.

Generally these lights are produced through rapid charge/discharge cycles inside a xenon gas tube.

In this article we will learn how to build strobe lights and generate same effect as discussed above.

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Replacing Xenon Tube With LEDs

Today’s modern high bright LEDs can produce light as sharp and intensified as the more conventional xenon tubes. Moreover strobe lights made up of xenon tubes or incandescent bulbs require very high voltage and high current respectively for the operation. LED strobe lights on the contrary require comparatively negligible power and are highly reliable. They come in many varied colors and thus have become more preferable. Let’s move on and see how we can build strobe lights used in police vehicles through a simple construction project.

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Parts List

IC 4017 = 1no.

IC 4093 = 1no.

R3 = 150 Ohms, ¼ watt, CFR

R1 and R2 = 100 K, ¼ watt, CFR

VR1 and VR2 = 1 M Pot. Linear,

C1 and C2 = 470 nF

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Circuit Description

The circuit description of the present circuit can be understood through the following points:

Gate N1 and N2 are configured as simple oscillators. These produce alternate logic hi and a logic lo at their outputs. These are also known as clock pulses.

The clock signal from the oscillator N1 is fed to the clock input of the IC 4017.

These clock signals are transformed into sequential high logic pulses by the IC 4017 through its output pins in the order of 3, 2, 4, and 7.You may refer to one of my previous articles regarding the pin outs of the IC 4017 for the ease of construction.

Looking at the circuit diagram you will find that the common cathode point of all the LEDs have been joined to the output of another oscillator (N2).

This makes the circuit very interesting. The LEDs are forced to flash at a rapid rate (adjustable) simultaneously as they shift sequentially at the outputs of the IC 4017. In simple words the group of LEDs is made to flash and “run" or “chase" simultaneously. This effect is actually responsible to produce a real police strobe light resemblance.

The “Chasing" and the “Flashing" effects are both adjustable using discrete potentiometers. These may be optimized in different ways to obtain visually rich strobe patterns.

This circuit may be used as LED strobe lights during fun gatherings in halls or homes to enhance the party mood. It may also be used in vehicles to attract attention, but mind you, the act may be illegal in some countries and prior permission may be required from the authorities.

Need more info regarding how to build LED strobe lights? Feel free to jot in your comments. (Comments are moderated. They do not appear instantly.)